Applicants claim, under 35 U.S.C. xc2xa7 119, the benefit of priority of the filing date of May 6, 1998 of a German patent application, copy attached, Serial Number 198 20 014.5, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
It is necessary in many cases to absolutely determine the position of a shaft within one revolution, as well as the number of revolutions. Multi-turn rotary encoders are employed for this purpose, such as those described in EP 0 715 151 B1 and DE 42 20 502 C1. EP 0 715 151 B1 corresponds to U.S. Pat. No. 5,734,266, the entire contents of which are incorporated herein by reference.
2. Description of the Related Art
The multi-turn rotary encoder in accordance with EP 0 715 151 B 1 is described on page 9 of the HEIDENHAIN Company Prospectus: Code-Drehgeber [Rotary Encoder], April 1997. Several code disks are connected with each other by a gear for the detection and differentiation of a plurality of revolutions of a shaft. Each code disk includes several code tracks with alternatingly arranged north and south poles. The code tracks are differently divided, for example, the coarsest one has only one north and south pole each, the next finer track has two north and south poles each, and the finest track has eight north and south poles each. The code tracks are scanned by Hall sensors. An absolute multi-digit code word is formed by the combination of the scanning signals of all Hall sensors, which indicates the absolute angular position of the code disk.
It is disadvantageous in connection with this multi-turn rotary encoder that a code disk with several code tracks must be used in order to generate a multi-digit code word.
In the multi-turn rotary encoder in accordance with DE 42 20 502 C1 several code disks are also respectively connected with each other by means of a reduction gear. Each code disk includes a magnetic drum with a single north and south pole. Two Hall sensors, which are arranged offset from each other by 90xc2x0, are provided on the circumference of the magnetic drum. The magnetic field of the magnetic drum, which passes through the Hall sensors, is radially oriented. An analog sine and cosine signal is generated in one revolution of the magnetic drum. The analog sine and cosine signals of all code disks are fed to an evaluation unit, which forms the multi-digit code word, which in turn indicates the absolute angular position of the code disk over several revolutions.
It is disadvantageous here that it is necessary to mount the Hall sensors individually on a plate.
An advantage and object of the present invention is based on creating a multi-turn rotary encoder which is simply constructed and can be manufactured cost-effectively.
This advantage and object is attained by a multi-turn rotary encoder that includes a first code carrier connected with an input shaft, a scanning device that scans the first code carrier and generates an absolute position of the input shaft within one revolution, and a digital code word is present at an output of the scanning device and a second code carrier for measuring the number of revolutions of the input shaft. A reduction gear is arranged between and coupled to the first and second code carriers. The second code carrier includes a magnetic body with at least one north and south pole and a substrate with a spatial arrangement of sensor elements integrated therein, which are sensitive to magnetic fields, is associated with the magnetic body. An evaluation circuit integrated into the substrate, wherein scanning signals, which are phase-shifted with respect to each other, from the sensor elements are supplied, and that the evaluation circuit combines the scanning signals in such a way that a second digital code word is present serially or in parallel at an output of the evaluation circuit. A combination logical device, which is supplied with the first and second digital code words and which forms a resultant multi-digit code word therefrom.
An advantage and object of the present invention reside in that all sensor elements for scanning one or several code carriers are integrated in one chip and therefore are extremely accurately aligned with each other and have the identical characteristics.